Never Use OvernightPrints.com, Ever.
How not to run a postcard-printing service.
1) Mail someone the wrong postcards (for instance, for a group exhibition in Wisconsin when the order was placed from Brooklyn).
2) When the customer calls to report the error, make her pay extra to have her new postcards delivered the following Saturday, since the postcards are needed that day, even though the mailing mistake was entirely the company's.
3) When the customer calls on Friday just to be sure the postcards will be delivered the following day, tell her there was an oversight and the postcards won't be delivered on Saturday afterall! As a minor concession, all of the shipping charges will be refunded. Plus she gets 20% off her next order (it'll never happen!) with OvernightPrints.com.
4) Don't give her any refund at all until she calls the next week to ask about it!
5) Only refund her half the charges, until she calls two days later to nag!